Conventionally, a semiconductor chip mounted on a lead frame or a printed circuit board or the like (hereinafter simply referred to as a “substrate”) is sealed with resin by employing resin-molding referred to as transfer mold. In transfer mold, a resin molding die is employed.
For the resin molding die, porous material can also be used. The porous material includes a filter layer capable of introducing air into the die or exhausting air from the die, as described in Patent Document 1. The filter layer has an air vent having a ventilating opening connected for example to a pump. The air vent has a surface connected to a surface of the die that has a communicating opening communicating with the ventilating opening. When the communicating opening is exposed to flowable resin the communicating opening prevents the flowable resin from flowing into the ventilating opening and permits the gas in the die to flow into the ventilating opening.
Furthermore, the resin molding die overlies a heater heating the flowable resin, composed of thermosetting resin, approximately at 180° C. to set the flowable resin to provide set resin. Consequently, the set resin seals the semiconductor chip mounted on the substrate.
A conventional resin molding die employing the above described conductive porous material has the following effects:
Initially, air or similar gas in a cavity can be externally exhausted. This can provide a resin molded product internally free of air bubbles or the like. Furthermore, after resin-molding when a molded product is released from the die, gas of high pressure is externally injected into the cavity. This can eliminate the necessity of employing an ejecter pin to release the molded product from a molding surface.
Patent Document 1: Japanese Patent Laying-Open No. 8-192438 (pages 6-10, and FIGS. 5, 7 and 10)